Irregular Division Research Articles

Time-Lapse Cinemicrographic Observations of Heated G1-Phase Chinese Hamster Ovary Cells: II. Cell Death, Fusion, and Multipolar Divisions

Two forms of irregular divisions, multipolar divisions and divisions followed by fusions, were evident in Chinese hamster ovary cells which were heated in the G1 phase of the cell cycle following s...

Growth characteristics and ultrastructure of protoplast type L-forms from streptomycetes.

L-form colonies from S. hygroscopicus, S. griseus and S. levoris were isolated after incubation of lysozyme protoplasts on an osmotically stabilized complex agar medium. Unstable and stable L-forms grow on solid and in liquid media. L-form colonies are 5-10 times smaller than normal colonies and show a typical morphology for each species. In ultrathin sections L-form cells are characterized by nucleoid areas with typical core-like structures, by a ribosome-rich cytoplasm with different inclusion bodies, and by a cytoplasmic membrane. Because there are no cell wall structures L-forms of the three Streptomyces species belong to the protoplast type. Analysis of cell size and cell shape shows a variation in diameter and a cell propagation by regular and irregular division- and budding-like processes. Many L-form cells contain more than two chromosomes. The results are discussed with regard to the cellular organisation of streptomycetes and the nature of the stable L-form.

Growth characteristics and ultrastructure of protoplast type L‐forms from Streptomycetes

AbstractL‐form colonies from S. hygroscopicus, S. griseus and S. levoris were isolated after incubation of lysozyme protoplasts on an osmotically stabilized complex agar medium. Unstable and stable L‐forms grow on solid and in liquid media. L‐form colonies are 5–10 times smaller than normal colonies and show a typical morphology for each species. In ultrathin sections L‐form cells are characterized by nucleoid areas with typical core‐like structures, by a ribosome‐rich cytoplasm with different inclusion bodies, and by a cytoplasmic membrane. Because there are no cell wall structures L‐forms of the three Streptomyces species belong to the protoplast type.Analysis of cell size and cell shape shows a variation in diameter and a cell propagation by regular and irregular division‐ and budding‐like processes. Many L‐form cells contain more than two chromosomes.The results are discussed with regard to the cellular organisation of streptomycetes and the nature of the stable L‐form.

Polyploidy in Sporobolus virginicus (L.) Kunth

Chromosome number and meiotic behaviour was examined in Sporobolus virginicus Kunth from south-eastern Australia. Var. minor Bail. forms a polyploid complex with diploid (2n = 20), triploid and tetraploid cytotypes. Meiosis in tetraploid plants of this variety is substantially normal, which indicates an alloploid origin. Var. virginicus, which has been found only in the tetraploid state, has irregular meiotic division, which suggests autoploidy. Most cytotypes were collected from sandy and well-drained situations along the coast. However, tetraploid var. minor plants were generally found in poorly aerated salt marsh swamps. This apparent edaphic adaption of tetraploid cytotypes may be important in explaining distribution patterns.

ABERRANT MICROSPOROGENESIS AND STERILITY IN IMPATIENS SULTANI (BALSAMINACEAE)

Three mutants of Impatiens sultani (named as ‘Orange', ‘Crimson', and ‘Pink') show an unusually wide spectrum of aberrations in microsporogenesis. These aberrations range from premeiotic cytomixis to meiotic and postmeiotic irregularities such as precocious disjunction, tripolar separation of chromosomes, chromosome bridges, various patterns of atypical cytokinesis, supernumerary divisions of the meiotic products, and irregular divisions in the microspore. As a result of these abnormalities Orange is partially and Crimson and Pink are completely pollen sterile. The stigmas of Pink, besides, do not support pollen germination. The failure of pollen germination is attributed to the defective stigmatic fluid of Pink, which, compared to that of Orange and Crimson lacks organic compounds absorbing UV light at 261 nm. This constitutive deficiency in stigmatic fluid appears to be a little investigated facet of female sterility.

Ascal cytology ofSordaria sclerogenia

Nuclear behavior during ascosporogenesis ofSordaria sclerogenia Fields and Grear was studied with the use of the HCl-Giemsa staining technique. Except for some spore abortion and occasional irregular mitotic divisions in the spore, the chromosome behavior was found to be compatible with that reported for other members of theSordariaceae and other pyrenomycetes with eight linearly arranged ascospores. A haploid chromosome complement of seven was found. The behavior of the centriolar-bodies during meiosis in this organism is discussed.

STUDIES OF MEIOSIS IN THE GENUS SAXIFRAGA OF THE PACIFIC NORTHWEST

A cytogenetic study of the genus Saxifraga in the Pacific Northwest has been initiated as a contribution toward a better understanding of relationships within the genus. The present paper reports work done on nine species or groups of morphologically similar species and varieties (each group termed a "plexus") which have so far been studied. The nine species or groups of species are S. tolmiei, S. bronchialis, S. integrifolia, S. ferruginea, the S. montanensis plexus, the S. occidentalis plexus, S. odontoloma, S. lyallii and S. mertensiana. Meiosis in pollen mother cells of one species was found to be generally regular, pollen fertility high. In every other species or plexus a variable and sometimes very high degree of meiotic irregularity was present. Pollen fertility was often much reduced. The cause of meiotic disturbances has not yet been discovered. Consideration is given to the ways in which the species may succeed in spite of reduced pollen fertility. Such irregular meiotic divisions would be difficult to use in cytogenetic studies as a standard for comparison with meiosis in artificial hybrids.

Morphological and Cytological Changes in Century Patna 231 and Bluebonnet 50 Rice Resulting From X‐Ray and Thermal Neutron Irradiation1

Morphological and cytological studies of one X/sub 2/ (maintained vegetatively) and 20 X/sub 5/ lines of Bluebonnet 50 and Century Patna 231 rice varieties obtained from seeds exposed to different dosages of x rays and thermal neutrons revealed a number of interesting and valuable mutant types. These included mutations of leaf size and color, growth habit, plant height and straw strength, particles, spikelets, flowering habit, and fertility. Some of the short-stature and other plants may have considerable economic value in breeding lodging resistant varieties. Cytological studies revealed that one plant was a tetraploid. Most plants studied were diploid but often had abnormal chromosome numbers or association. Univalents, trivalents, and quadrivalents were common but fragments. asynapsis, knot formations, irregular division, bridge formations, and differences in pollen grain size were observed. There was a positive correIation hetween quadrivalents in P.M.C. and pollen sterility and between pollen and spikelet sterility, although there were some unusual exceptions to this. (auth)

Heavy water inhibition of cell division: an approach to mechanism.

ABS>At concentrations higher than about 75%, deuterium oxide blocks cell division in the eggs of the sea urchin Arbacia punctulata and in those of the annelid Chaetopterus pergamentaceus. The block is reversible, although cells that have been kept is a deuterium-rich medium for long periods relative to the time for one mitotic cycle may show multipolar and irregular divisions after removal to normal water, and may subsequently cytolyze. The antimitotic action is manifested at all stages of the mitotic cycle and, to a significant extent, during cytokinesis. An important feature of the mitotic block is that it becomes effective almost immediately after the cells are placed in D2O and is quickly reversed when the cells are washed free of D2O. Whereas D2O blocks mitosis at all stages it does not destroy the achromatic apparatus, nor does it cause wholesale regression of cleavage furrows. Instead, it exerts a powerful stabilizing effect upon these structures. This appears to be related to a sharp and reversible increase in cytoplasmic viscosity evoked by immersion of nondividing cells in D2O. Examination of a number of alternative explanations of the effect leaves as the most useful working hypothesis a rigidification of the mitotic apparatus, possibly throughmore » a small increase in the strength of individual hydrogen bonds which cross-link macromolecules or small particles. For large, multiply cross-linked structures, such changes for individual bonds would produce very large cooperative effects in the direction required by the data.« less

Meiotic irregularities in hexaploid oats: II. A cytological survey of the variety Picton

SUMMARY1. Picton, a winter-hardy variety of oats selected from the cross Argentine x Grey Winter, contains plants which have irregular meiotic divisions.2. Two types of irregularities were observed: first, univalents and the products of their division; and secondly, bridges and fragments at both first and second divisions.3. Plants selected for a low frequency of irregularities produced offspring with a low frequency of irregular divisions. On the other hand, plants with regular divisions were also obtained from parents which had a high frequency of irregularities.4. It is pointed out that the genetical effects of bridge chromatid formation and breakage is the production of gametes deficient for chromosome segments. There is some evidence that chlorotic plants are produced when such deficiencies become homozygous.5. It is suggested that the meiotic irregularities produce a certain degree of heterozygosity which may make Picton more adaptable, and at the same time give it a certain degree of hybrid vigour.

CALIBRATION OF PRISMATIC COMPASSES

Apart from “stickiness” of the suspension and looseness of the sights, prismatic compasses are subject to three internal sources of error:- <list list-type="roman-lower"> <list-item>Collimation error. This may be caused by <list list-type="alpha-lower"> <list-item>magnetic axis not being parallel to the zero line of the graduated circle;</list-item> <list-item>line of sight not passing through the axis of rotation.</list-item> </list> It is unnecessary to aftempt to distinguish between the above faults, which introduce constant errors into the compass readings.</list-item> <list-item>Eccentricity error. This is caused by the axis of rotation failing to pass through the centre of the graduated circle. This introduces an error into the compass readings of E sin θ cosec I°/R where E is the eccentricity, R the radius of the graduated circle and θ the angle between the line of sight and the line joining the centre of the circle to the axis of rotation. Eccentricity error is completely eliminated by observing both forward and back bearings, but this is not always practicable.</list-item> <list-item>Irregular division of the graduated circle. This error is negligible in any modern compass.</list-item> </list>

The Chorus of Alcman'sPartheneion

The irregular division of vv. 35 sqq. between two semi-choruses seems to bo widely accepted and approved.2 I wish first to discuss the obvious objection that such an irregular division is unparalleled in a strophic chorus,3 and secondly to show that the reasons advanced for the division are themselves insufficient.

The Progeny of Tetraploid Tomatoes (Preliminary report)

Forty heteroploid tomatoes arised out of five hundred seeds, which were obtained from the regenerated tetraploids produced by the decapitation-method. They could be already noticed in the seedling stage for the slowness of germination and the abnormality of cotyledons. The dwarfness and bushy form are two remarkable characteristics of the mature plants and their fruit-setting is very rare or none. The somatic chromosome numbers of the heteroploid plants so far examined are 49, 50, 51, 52, 53, and 54; namely 4n+1, 4n+2, 4n+3, 4n+4, 4n+5 and 4n+6 respectively. The heteroploidy may be caused by the gamates, which have super diploid chromosome numbers on the consequence of irregular division of pollen mother cells in the tetraploid tomatoes.

KARYOTYPES IN &lt;i&gt;RUMEX ACETOSA&lt;/i&gt; L. AND THEIR GEOGRAPHICAL DISTRIBUTION

Three new Karyotypes of Rumex acetosa were discovered. These are type VI (10i+2J), type VII (10i+2T) and type VIII (8i+2J+2T) (Table I., Fig. 1.). Accordingly the karyotypes of Rumex acetosa are 8 in all. The geographical distribution of the three karyotypes in Rumex acetosa has been studied. Type I was found to be distributed in the northern part of Japan proper, Corea, Kurile Islands and Formosa, and type II in the middle part and type III in the southern part of Japan proper. Owing to the scanty materials the distribution of the remaining karyotypes (types IV-VIII) can not easily be determined (Fig. 2.).Meiosis in some hybrids between these karyotypes was studied; some of these showed rather irregular divisions while others were quite normal.The author has arrived at the following conclusions on the origin of the different karyotypes in Rumex acetosa:-I. The existence of many triploid intersexes in wild and in cultivated plants plays an important part about the origin of karyotypes. Meiosis is more irregular in the triploid intersex than in the triploid male plant or in other autotriploid plants.II. Consequently new shapes of chromosomes which were not found in the mother plant were found in the progenies of triploid intersexes (Fig. 3-1).III. Plants with several fragments of chromosomes were often found in the wild. Usually we observed some large J-or V-shaped chromosomes in these plants (Fig. 3-2). Fragmentation of chromosomes was often observed in the course of PMC divisions of some hetero- as well as euploid plants of this species.IV. Two plants in which the segmental interchange of chromosomes and simple translocation had occured were found. Both are female so that I could not study the ring of four expected. But judging from the shape of somatic chromosomes I can easily decide which chromosomes have changed. The interchanged chromosomes are shown in dots (Fig. 3-3 F' C', 3-4 B' D').V. The chromosomes of new shape whose origin is undetermined are labelled with question marks in figures. These chromosomes may be explained as the results of complicated changes of chromosomes in the progenies of triploid intersexes. These structural changes in chromosomes perhaps give rise to the differentiation of karyotypes.

Microsporogenesis and Embryogeny in Certain Species of Bromus

1. Bromus marginatus and B. rubens are octoploid and tetraploid respectively; B. villosus is variable between octoploid and decaploid. 2. Polyploidy and other irregularities in the maturation division indicate that these species may be hybrids. 3. Lagging bivalents are found in B. villosus and B. marginatus. An irregular homeotypic division, showing much lagging and extrusion, occurs in B. villosus. 4. Varying types of chromatin extrusion are found in all three species, together with polycary and sterile pollen. 5. No examples of cytomyxis were observed. 6. Megasporogenesis and embryo sac development appear to be rather typical for the Gramineae. 7. Antipodals generally vary in number from five to eight, with a maximum of ten seen in one instance. Their nuclei are large, are often organized into cells, and finally occupy a lateral position just below the center of the sac, in which position they undergo dissolution, after an existence considerably longer than that characteristic of smaller cells.

Studies on certainPetunia aberrants

After crossing a tetraploidP. violacea (28 somatic chromosomes) with a diploid (14 somatic chromosomes) which differed in certain characters from the tetraploid, progeny were obtained with 28 (tetraploid), 27 (hypotetraploid), 21 (triploid), and 20 (hypotriploid) chromosomes, and diverse morphological characters. The appearance of the plants with one less chromosome than the complete tetraploid or triploid set is attributed to the irregular meiotic divisions in the tetraploid mother plant. The ratio of formation of 13- and 14-chromosome gametes in this plant as a result of non-disjunctions in the reduction division was calculated to have been 1:6. Flower buds of the progeny studied during meiosis showed meiosis to be accompanied by various degrees of irregularities. This process was almost regular in the tetraploids, only slightly less so in the hypotetraploids, quite irregular in the triploid, and most irregular in the hypotriploid. The plants with 28 and 27 somatic chromosomes were self-fertile, those with 21 and 20 were self-sterile but set seed when pollinated with the tetraploids, and in the case of the triploid with the hypotetraploids also.

REGENERATION AND REGULATION IN PARAMECIUM CAUDATUM

1. When the anterior end of the cell was removed by a transverse cut through the peristome just in front of the macronucleus, thirty-four per cent. of the fragments regenerated the lost end and divided normally. When the posterior end was removed by a similar cut, back of the mouth, sixty-two per cent. of the nucleated fragments regenerated the lost end and formed a normal race.2. Removal of the anterior end resulted in irregular division in fifty per cent. of the nucleated fragments, while removal of the posterior end caused irregular division in only twenty per cent. of the pieces.3. Paramecia cut in half transversely usually die as the nucleus is forced out by the pressure of the knife. When the nucleus remains in one of the halves regeneration is followed in that half by normal division.4. Monsters develop from fragments composed of more than half of the protoplasm of a normal Paramecium, but never develop when a cell is cut exactly in half.5. A fixed division plane is present in the normal cell as early as two and a half hours after fission. It is possible in vegetative cells, where fission has been delayed for a period, that more than one plane is laid down. This would account for the fact that after cutting off one end of the cell several divisions follow in quick succession.6. The power of regeneration varies in different races, and in different individuals of the same race. It is the index of the condition of the cytoplasm.7. The removal of a portion of the cytoplasm does not result in the production of smaller individuals. After several generations have been produced the normal size is regained.

A CRITIQUE OF THE SPOROZOAN THEORY OF MALIGNANT NEOPLASMS FROM A MICRO-TECHNICAL STANDPOINT.Read in the Section on Surgery and Anatomy at the Forty-fifth Annual Meeting of the American Medical Association, held at San Francisco, June 5-8, 1894.

The present condition of the sporozoan theory of the etiology of malignant tumors in man and the higher animals is one of much confusion. The student of this subject is confronted by a multitude of imperfectly digested contributions from investigators of all ranks of excellence. It is astonishing to note the variety of objects which have been assigned to the class of cancer parasites by over enthusiastic workers. Almost every object which presents itself in the histologic study of malignant tumor tissue has been described as the earcinoma organism, from the blood elements on the one hand, to the tumor cells themselves, on the other. Red blood cells, leucocytes, blood plates, invaginated cells, endogenous cell formations, irregular nuclear division products, metabolic cell products, cell-degeneration products, capillaries filled with blood corpuscles, and other objects, familiar to the careful histologist, have been interpreted as parasites by some investigator in this field. The